Rule of Sixes

The rule of sixes describes a method of determining the distance from which a shotgun was fired. In 1963, shotgun wounds were classified into three types based upon distance and penetration. The distances of six feet, less than six yards, and beyond six yards originally identified by firearm experts brought up the name "rule of sixes." At close range (less than six feet) a shotgun wound appears as a central hole. A blast fired from a distance of up to six yards leaves a central hole with satellite entry wounds. Beyond six yards, the wound appears as only a pattern of scattered shot, with no central hole.

In terms of forensic investigation, the determination of the gun's position is the specialty of both the firearms expert and the pathologist. If the gun is pressed close against the skin, all the little shots are concentrated in one place, leading to large wounds. At fairly close range, the shot begins to expand. At about two feet away, the wound begins to look like a large central hole with a few little holes surrounding the edge. Beyond four or five feet, the shot disperses and is more likely to make many smaller wounds and less likely to be fatal.

The wound itself can give important indications on the position of the gun. If the gun is pressed close against the skin, there is a small ring of soot, which is burned into the flesh and cannot be removed. The gun that was fired a few inches away leaves a large ring of soot, since it had the space to disperse and was not embedded. If the gun was held at an angle, the ring of soot will be distorted in one direction.

The distance at which the gun was still close enough to leave residue is called the intermediate range. Tattooing is a pattern of tiny orange-brown lesions on the skin made by a reaction to the gunpowder. It occurs before death, so is an indication that the person was alive at the time they were shot. If the victim was dead at the time of the shooting, there will still be powder marks, but they will be grey-yellow in color. Size and position of the soot can be used to determine the direction and distance of the gun. However, this is affected by the type and make of gun, so it is helpful to have that information first. As the gun gets further away, the area covered by soot becomes wider but the concentration becomes less dense. At long-range distance, no powder marks are generated. The only mark is the bullet hole.

Because distances are often unknown, the groups defined by the "rule of sixes" were reclassified in 1993 by pathologists according to the patterns of pellet scatter. Type I patients had >25 cm (10 inches) of scatter, Type II had <25 cm (10 inches) but >10 cm (4 inches), and Type III had <10 cm (4 inches). In terms of forensic pathology , pellet scatter proved to be a more accurate system, as well as more useful to physicians in determining patient treatment and recovery prognosis for persons with shotgun wounds. The term "rule of sixes," however, was kept.

see also Firearms; Gunshot residue; Pathology; Wound assessment.